Establishment of an animal model of shaft femoral pseudoarthrosis in rabbits.

PURPOSE: This study aimed to establish a novel rabbit model of femoral shaft pseudoarthrosis.

METHODS

Twenty-four New Zealand White rabbits were divided into three groups. The model involved creating a femoral bone defect stabilized by an external fixator. In the control group, bone healing was assessed at 8 weeks. In the P1 and P2 groups, muscle interposition was added at the defect site, and healing was evaluated at 8 and 12 weeks, respectively. Bone healing was assessed through radiographic, macroscopic, histologic, and molecular analyses, including qRT-PCR for collagen type I (COL1A1) and RUNX2 mRNA expression.

RESULTS

Complete bone consolidation was observed in all rabbits in the control group. In contrast, the P1 and P2 groups showed radiological signs of pseudoarthrosis, including persistent inter-fragmentary gaps, medullary canal obliteration, and bone end resorption. Histological analysis revealed fibrocartilaginous tissue and residual muscle at the defect site. Compared to the control group, both P1 and P2 groups showed significantly less bone formation and increased fibrocartilaginous tissue. No significant difference was found between P1 and P2 in terms of fraction of bone and fibrocartilaginous tissue. Molecular analysis supported these findings, with significantly reduced expression of COL1A1 and RUNX2 in P1 group.

CONCLUSION

We successfully established a reproducible model of femoral shaft pseudoarthrosis in rabbits, which can serve as a platform for evaluating new therapeutic strategies.